drawing utensils
Feathers
The tracing tools traditionally used in technical drawing are pencils and technical pens.
The pencils normally used are mechanical pencils, with standardized thicknesses and lead types. Typical line widths are 0.18 mm, 0.25 mm, 0.5 mm and 0.7 mm; and the hardness normally varies from HB to 2H. Softer leads give better contrast, but harder leads provide a cleaner line (i.e. less prone to smearing) but not as visible. The low contrast of pencil marks is generally problematic when the original has to be photocopied, but new scanning copying techniques have significantly improved the final result. Paper or plastic surfaces require their own special lead types.
In many cases, the final plans are drawn with ink on plastic supports or on translucent paper, generally using sets of technical pens with strokes of different standardized thicknesses. These pens have an ink reservoir that feeds a pointer, formed by a hollow metal cylinder, into which a thin metal filament attached to a lead plunger can slide. The ink is absorbed by capillarity between the filament and the inner wall of the tube, preventing an excessive amount of ink from being released. When you lightly shake the pen up and down, the weight of the plunger releases the inner end of the tube, reactivating the ink feed. Originally, the tanks were filled with ink that was supplied in bottles or small containers; although more recent models use disposable cartridges.
Each pen is equipped with a pointer of a certain width. These line widths are standardized: pen sets generally used in Finland include the thicknesses 0.13 mm, 0.18 mm, 0.25 mm, 0.35 mm, 0.50 mm and 0.70 mm; although it is also common to find thicknesses graduated in tenths of a millimeter (0.10 mm, 0.20 mm, 0.30 mm... 0.80 mm, and even up to 1.00 mm). Styluses for drawing on paper and plastic are different, because plastic requires a harder type of stylus. To function properly, they require regular maintenance, especially pens of the finest thicknesses, whose metal filaments are so extraordinarily thin that they can break relatively easily if the ink dries inside the pointer.
drawing board
The drawing board is an essential tool, since it is necessary to hold and keep the paper aligned on a completely flat surface so that the drawing can be made with the required accuracy. Generally, to draw and take measurements, different types of auxiliary rulers are used, mounted with sliding or articulated frames on the drawing board, which is normally installed on an orientable and height-adjustable pedestal.
There are also smaller drawing boards, designed to be used on normal desk tables.
In the 19th century, the paper became moist and its edges stuck to the board. After drying, the paper was perfectly flat and smooth, with the drawing cut out once completed.[4] The paper was also secured to the drawing board with pins or thumbtacks, or even with clips or clips.[5] In more recent times, self-adhesive tape was used to hold the paper, including the use of adhesive dot dispensers. Some drawing boards are magnetized, the paper then holding itself thanks to the attraction on a series of steel bands. Another common system on boards with a slight inclination was to place lead weights covered in leather in the four corners of the paper.
Tables used for overlaying designs or in animation may include pins or holding bars to ensure perfect alignment of the drawing's multiple layers.
To facilitate perfect visibility of the work area, the drawing tables were equipped with a flexo-type lamp, mounted on the upper edge of the board with an articulated arm, so that it did not dazzle the draftsman and avoided the problem of shadows cast by the hands on the drawing.
T-rule
T-rulers use an edge of the drawing board as a support, making it easier to draw horizontal lines and allowing other drawing instruments to be aligned. Triangular templates made of wood, metal or plastic with angles of 30° and 60° or with two 45° angles make it easy to draw lines with these common inclinations, which can also be drawn with a protractor adjustable between 0° and 90°.
An alternative device is the parallel ruler, which is permanently attached to the drawing board by a set of cables and pulleys that make it possible to move it parallel over the entire work surface. The technigraph ended up replacing parallel rules in professional delineation.
Technographer
A technigraph is a device that is mounted on the drawing board. It has a mechanism with a system of springs and shock absorbers designed to be able to adjust it precisely and smoothly in any position and angle on the drawing.[6].
There are two main types of apparatus: with the arm swinging on an articulated parallelogram; or sliding and pivoting on a vertical rail. The accuracy of the movement of the articulated arm is best in the center of the board, decreasing towards the edges, while the sliding arm has a constant accuracy over the entire board. Both types of devices have an adjustable rotating head, where rules are articulated whose inclination can be adjusted on the scale of a protractor.[7].
The technigraph facilitates the task of drawing parallel lines on the paper, as well as precisely adjusting the desired angles between the two rulers articulated on the head, which can also be used as a support for special rulers and lettering templates. The head rulers can be replaced, such as if different graphic scales need to be used.
Some boards mounted a parallel ruler and a pantograph, a device used to copy drawings in an adjustable scale ratio.
Graduated rules
The graduated rulers used in technical drawing are normally made of polystyrene, and are of two types depending on the design of their edge. The straight-edged ones can be used with pencils or pens with dense ink, while when using technical pens the edge has to be stepped to prevent the ink from dispersing by capillarity between the paper and the ruler (producing what in draftsmen's jargon was known as a "beard", or more commonly, a "blot").
A scalemeter is a triangular prismatic ruler, which includes six scales graduated simultaneously (two on each edge). A typical combination for measuring details on construction plans is 1:20, 1:50, 1:100, 1:25, 1:75 and 1:125. There are also particular rules from different countries, such as those graduated in inches. Currently they are manufactured with different plastics, although in the past they were made of hard woods. Likewise, there are pocket versions, with the scales printed on elongated flexible plastic sheets, which can be deployed around the axis on which they are mounted.
Compass
Compasses (instrument) are used to draw circles or circular arcs. The most common type has two straight "legs" (also called "arms") joined by a joint; One of the legs ends in a sharp point, and the other holds a technical pen, a pencil or any other element capable of marking the paper.
They were usually marketed as compass sets, in wooden or plastic cases, which usually contained anything from a single normal compass (with its ruler) to sets of numerous pieces of different types (compass, point compass, mustache and crazy mustache). With the appearance of technical pens, heavier than a pencil ruler, the compasses became more rigid and larger, and mustaches equipped with a special device to hold the pens were common. Among the best-known manufacturers of compasses were the Swiss company Kern & Co, and the German companies E. O. Richter,[8] Faber Castell and Staedtler.
When it has two needles, it is called a "point compass" or "dry point", used to transfer measurements between different parts of a drawing.
Another type, called "mustache", is an adjustable compass (its silhouette is similar to a letter "A") whose opening can be adjusted by turning a screw that goes through its two legs. On the other hand, when it is necessary to draw arcs with a very large radius, extensions are available that can be attached to the instrument to increase its working radius. Circle templates are also often used (especially for diameters between 1 mm and 25 mm), which are more convenient and faster to use than the compass for these small sizes.
Before the invention of technical pens, it was not possible to stencil small details such as letters or circles. To draw very small circles (less than 5 mm in diameter) with a pencil, the "crazy mustache" was used, a special compass in which the leg with the drawing tool can pivot freely on the leg with which the center of the circle is marked. It was a difficult instrument to use, as it required applying a blow with just enough force to the free leg so that it made at least one complete revolution without spilling the ink from the pencil grip as a result of the rotation.
Burmester Insoles
Burmester templates are made of wood, plastic or celluloid. Some of these rules also include cut-out profiles inside. They are used to draw curves that cannot be drawn with a compass. To do this, the curve is drawn freehand with a pencil through the known points; looking for the longest possible section of one of the templates that exactly matches the curve drawn by hand. Finally, relying on one or several curved segments of the templates, it is possible to label the desired continuous curve.[9].
Flexicurve
Another method that allows drawing smooth curves are flexicurves (flexible curves, formed by a rubber-coated lead rod, easily moldable), with which it is easier to follow the desired curve, although if the instrument is not in perfect condition, it may retain remaining deformations, which distort the smoothness of the desired profile. If an elastic rod is used (but not plastic, that is, it does not retain deformations) then it must be placed in position using small weights.
Templates (perforated pattern system)
These types of templates contain a series of pre-sized holes at a certain scale, facilitating the drawing of letters, symbols, signs, silhouettes and other graphic elements. Its main advantages are its price (the usual models molded in plastic are quite economical) and its simplicity of use (any artist with a minimum of skill can master this technique in a very short time).
Letter templates are used to label texts, including digits and spelling characters. Normalized fonts (for example, DIN or ANSI) and letter heights are typically used, each suitable for a given technical pen thickness (typically 1.8 mm, 2.5 mm, 3.5 mm, 5.0 mm, and 7.0 mm). Larger font sizes can also be used for labeling with other drawing utensils, such as markers or pens.
To draw arcs and circles, templates with sets of circular holes of different sizes are used. There are also templates with other geometric shapes, such as squares or ellipses (those typical of the isometric perspective are common), as well as many other types for various specialized purposes, such as architecture (including doors with their opening arches, equipment and furniture) or engineering (with traffic signs, or the symbology of electronic circuits).
Templates (engraved pattern system)
In the mid-1930s, the American company Keuffel and Esser (founded in the second half of the century by two German immigrants), devised a novel lettering system commercially called "Leroy".[10] The procedure was based on a small pantographic mechanism (colloquially called in Spanish the "crab"), with which the letters engraved in bas-relief on a strip were reproduced on paper (instead of perforated, as in the other type of templates) when moving over them with the pantograph pointer.
This system, which became very common among professional draftsmen, produced text of high graphic quality, and had the advantage that the templates could be used with pens of different thicknesses (unlike what happens with die-cut templates, the same letter height could be used either with a thin pen, which produced normal text; or with a thick pen, which produced bold text), which made it possible to enrich the typography of the plans. Its main drawbacks were the price of the equipment and a somewhat longer learning period, although these disadvantages were ultimately compensated by the better quality of the text and the high productivity of the procedure once the technique necessary for its use was mastered.
There was a wide catalog of power strips with different fonts, which were normally kept together with the pantograph in a wooden case.
Perspective machines
They are instruments designed to facilitate the representation of three-dimensional objects on the drawing plane.[11] Through an optical system of superposition of the real image and the image of the drawing board, they allow perspectives of three-dimensional objects to be drawn freehand.